4 Link Rear

Anonymous · Post by **Anonymous** » Wed Jul 07, 04 3:21 pm

My Charger is coming off the road before I do the CH Hardtop now, because I don't think it'll last that long.

I am going all out, and want to redesign the rear suspension to a 4 link system with a panhard rod to improve handling (going Pro Touring). I want to keep the solid axle because of the extra strength it provides over an IRS system with the sort of HP I want to build into the motor.

On the front I intend to use the Alterkation kit once Bill Reilly has developed the RHD version on Tweety (see bigblockdart.com), and it only seems sensible to improve the back aswell.

Has anyone ever done a similar project? If so can you give me any pointers and pitfalls?

I don't want a Drag Race narrow Ladder bar setup, I want a good street setup to improve grip at the back under high side force conditions.

Whilst I'm on it. Does anyone have technical drawings of the back end of the A body or Aussie Charger? I want to plug it into Catia V5 to help me: a) learn how to use Catia properly, and b) calculate the correct setup for the car.

Dave-R · Post by **Dave-R** » Wed Jul 07, 04 4:23 pm

Don't throw the ladder bar idea straight out of the window without considering it carefully.
It has a lot of redeeming features and is CHEAP and SIMPLE compared to other systems.
I have known a few street driven cars with ladder bars and their owners always said the handled OK although I never drove one myself.

Anyway. Leaf springs and a pinion snubber or slapper bars do just as good a job at streetable power levels. Why bother with anything else?

Anonymous · Post by **Anonymous** » Wed Jul 07, 04 5:33 pm

I haven't thrown the idea of ladder bars out I'm just not keen on the very narrow setups you see on some drag cars. I believe a wider linkage setup would give far better stability. If ladder bars can be worked into this then all the better.

I'm trying to get the rear handling characteristics to behave better under cornering loads. Slapper bars, a rear sway bar etc would improve this but I think it'd still suffer from not having enough rear grip.

Blue · Post by **Blue** » Wed Jul 07, 04 7:34 pm

If it was me I'd stick with leaf springs and work out a watts linkage set up, with the the right spring rate a good set of gas shocks and decent wheels and tyres I think you'd have a good handling set up. I know this is all old technology but it can be made to work so why make life hard for yourself? Try and find out some info on Richard Eherenberg's green brick valiant, that thing out handles many modern cars with a load of old tech!

Dave-R · Post by **Dave-R** » Wed Jul 07, 04 8:14 pm

All I have is gas shocks, poly bushings in the spring eyes and a rear sway bar. It handles well. I am thinking of adding a Watts linkage but waiting to hear from the chap on here that has one already!

For traction on the strip the pinion snubber pushes the wheels down for grip and tries to lift the front of the car thus moving the center of gravity rearwards. As Blue says anything more is OTT unless you are making HUGE power.

Ladder bars (if you insist on having some) do this better (I think?) because they work like longer levers?

A simple long tube with a bushing at each end will sufice for a 'ladder'. Just mount one end to the bottom of the axle housing and the other to a point on the chassis further up the car. You should use a Panhard rod as well though because sideways movment could damage the rod ends.

Here is a scan of a diagram to work out ladder bar length. I also include photos of a Panhard rod and a Watts linkage.

Anonymous · Post by **Anonymous** » Wed Jul 07, 04 9:08 pm

Hmm,

This has got me thinking now

. Have you got any more diagrams etc that could help me make up my mind on this?

Dave-R · Post by **Dave-R** » Thu Jul 08, 04 8:29 am

Do I look like a freaking library? - Don't answer that!

Just do what your Uncle Blue says and keep it simple. Pointless having a suspension that will plant 800hp if you only have 300.

Blue · Post by **Blue** » Thu Jul 08, 04 9:39 am

For a handling application I would forget about ladder bars, they are excellent for the strip but don't allow the suspension to "lean over" enough for fast cornering. What happens is the suspension binds up and the axle brackets will crack and eventually fail, I have seen this happen on 2 cars locally. You can use ladder bars on the street but you need to adjust you driving style to suit. A simlar problem can arise with a panhard rod, this too can bind up if you have a lot of suspension travel ( which leaf spring cars usually do), so I think the watts linkage is a better idea as it allows alot of suspension travel but always positivly locates the axle transversely. It is far better to start out "tweaking" to stock set up as you are learning all this stuff and keep the car on the road as much as you can, rather than going all out with a completely different set up that will require major chassis and floorpan modification, much time and expense and the car off the road for a long time, and believe me I know about that! Keep it simple and keep it on the road!

Dave-R · Post by **Dave-R** » Thu Jul 08, 04 10:46 am

What if you use rose joints at the bushings John? Would that not get rid of the binding problem?
I know they would not insulate vibration very well.

Ivor · Post by **Ivor** » Thu Jul 08, 04 12:42 pm

If it helps you to make your mind up, I had rose jointed radius rods and a Panhard rod on the beam front axle I fitted to my Ch*vy powered Cresta.

It kept everything in a straight line, but the ride was like being dragged naked in a coal scuttle down a cobbled street...then the Panhard rod mounting eventually cracked and broke off...you don't want to know the rest of the story!

I agree with Blue, keep it simple, keep it strong and think about using isolastic type bushes.

Anonymous · Post by **Anonymous** » Thu Jul 08, 04 12:45 pm

Going Pro-touring? Nice one. does that mean some nice big wheels too?

I'm with John on this, watts linkage sounds like a good start. Rover SD1's come with these from the factory.

Can still be found in scrappys, and come with rubber bushings rather than rod ends, ideal for a street car. You can even chop off the brackets from the floor to make mounting it easier.

Philth · Post by **Philth** » Thu Jul 08, 04 1:09 pm

FWIW the 1600E 'Tina (and MK1/2 Lotus) has radius arms on the rear axle and, with gas shocks and poly bushes, handles perfectly and is very controllable. That's the one thing that I really liked about my 'E'.

Also, a stiffer chassis can vastly alter the handling characteristics of a car (boxed areas that were once open, chassis tie-bars, etc). EG if I jack up one corner of my daily driver (not telling you if you don't know!) , the only wheel left on the ground is the wheel in the opposite corner! The degree of body flex can be confirmed by how tighter or looser a door can become to open/close on its catch once the vehicle is jacked. Try it!

Dave-R · Post by **Dave-R** » Thu Jul 08, 04 1:09 pm

Roger wrote:Rover SD1's come with these from the factory.

Really? Interesting.....It has been a very very long time since I climbed about in a scrap yard. Maybe I should have a look around.

Blue · Post by **Blue** » Thu Jul 08, 04 1:18 pm

Both the ladder failures I have seen were rose jointed Dave. If you look at a ladder bar set up from the rear, as the body tries to lean over as you corner one ladder bar would have to go up and the other would have to go down, there is nothing in the system to allow this to happen and in this situation the rear suspension is in bind so something has to give. Same thing can happen with a panhard rod if it runs out of travel ( and it's arc of travel is fairy short), it will either be trying to pull against or push against the leaf spring causing a bind and it will eventually fail no matter what type of bush you were useing. I think panhard rods are best suited to coil over suspensions that have far less travel than a leaf spring does. A well designed watts linkage will allow the suspension to do it's thing but still stop any sideway's movement of the axle at all times, so I think that's the way to go. A rose joint will feel harsher for sure but if it's ultimate handling you are after it, that would be the way to go.

Blue · Post by **Blue** » Thu Jul 08, 04 1:22 pm

Yes a good point Phil! no point having a good suspension if the body just twists instead undoing all you hard work!